About ConvertSheet
Empowering analysts, developers, and everyday users with fast, professional data tools that run 100% locally on your device.
The Status Quo is Broken
Most online file converters upload your confidential spreadsheets, tax forms, and company datasets to unknown third-party cloud servers. Your files sit in unencrypted buckets, get logged, and pose major compliance risks under GDPR, HIPAA, and CCPA.
The ConvertSheet Solution
ConvertSheet leverages modern browser capabilities — WebAssembly (WASM), Web Workers, and HTML5 Blobs — to execute SQL engines and file compilers directly on your machine. Your data never touches a server.
Built by Priyanshu Rawat
Software Engineer • WebAssembly & Distributed Systems
I started ConvertSheet out of pure frustration with modern web utilities. As a software engineer working with high-volume datasets, customer transaction logs, and internal accounting spreadsheets, I found it unacceptable that converting a .json or .csv file to Excel required uploading sensitive company data to an anonymous third-party server.
With the maturity of WebAssembly (WASM), browsers are now fast enough to execute native C++ databases and columnar query engines locally. By embedding DuckDB, SheetJS, and dedicated Web Workers into ConvertSheet, we created a suite of converters and financial engines that are mathematically rigorous, blisteringly fast, and completely confidential.
Under the Hood: How We Build
Engineered with industry-standard open source libraries
Provides analytical columnar database queries, Parquet parsing, and NDJSON streaming right inside your browser memory without memory leaks.
High-performance spreadsheet generation (.xlsx, .csv) and zero-upload PDF manipulation engines running in dedicated Web Workers.
Fully static HTML pre-rendering with instantaneous client-side navigation, mobile responsiveness, and dark mode theming.
Installable as a desktop or mobile application with service worker asset caching, enabling 100% offline usage on flights or remote networks.